The flux of dissolved inorganic nitrogen(DIN),predominantly nitrate(NO_(3)^(-))and ammonium(NH_(4)^(+)),from land to coastal waters via rivers is commonly estimated simply by multiplying water flux with nitrogen conce...The flux of dissolved inorganic nitrogen(DIN),predominantly nitrate(NO_(3)^(-))and ammonium(NH_(4)^(+)),from land to coastal waters via rivers is commonly estimated simply by multiplying water flux with nitrogen concentration.Understanding DIN fluxes in gated estuaries is critical as these systems often serve as hotspots for nutrient transformations,influencing coastal water quality and ecosystem health.However,the subsequent interactions involving NO_(3)^(-)and NH_(4)^(+)adsorption or desorption on suspended sediments are often overlooked.To better understand the impact of these interactions on the overall NO_(3)^(-)and NH_(4)^(+)sorption or desorption and subsequently,the mobility and transport to the coastal zone,we conducted a series of NO_(3)^(-)and NH_(4)^(+)adsorption and desorption experiments.These experiments involved varying suspended sediment concentrations,particle sizes,salinities,and sea-salt ions to assess their potential effects.Results indicate that desorption of NO_(3)^(-)and NH_(4)^(+)from suspended sediments is more prominent than adsorption,with NH_(4)^(+)desorption being particularly significant.Notably,at low suspended particle concentrations and high salinity,NH_(4)^(+)desorption from sediments increased markedly,which further amplified in polyhaline conditions.This effect could result from ion pairing between NH_(4)^(+)and seawater anions,along with competition from seawater cations for sediment cation exchange sites,enhancing NH_(4)^(+)diffusion from estuarine sediments,and the elevated NH_(4)^(+)release could promote DIN transport to nearshore waters,especially in gated estuaries where sediment resuspension occurs.Given the critical role of NH_(4)^(+)in estuarine nitrogen cycling,ignoring these dynamics could lead to underestimations of DIN transport in river-estuary systems.Therefore,incorporating sediment dynamics into DIN flux estimations is crucial for accurately assessing nitrogen transport in gated estuaries.展开更多
In recent years,environmental DNA(e DNA)has garnered significant attention as a novel tool in biodiversity monitoring,recognized for its efficiency,convenience,and non-invasiveness.Despite its extensive application in...In recent years,environmental DNA(e DNA)has garnered significant attention as a novel tool in biodiversity monitoring,recognized for its efficiency,convenience,and non-invasiveness.Despite its extensive application in various ecological studies,such as conservation,invasion biology,biomonitoring and biodiversity survey assessment,its use in avian monitoring remains in its infancy.This review critically examines the potential and limitations of e DNA technology for avian monitoring,focusing on current advancements and ongoing challenges in this emerging field.Water and air are the primary environmental media for collecting avian e DNA,although other sources like spider webs and plant flowers have been explored as well.Notably,airborne e DNA has been reported to capture the highest diversity of avian species.While avian e DNA technology has shown promise for monitoring rare and endangered species and assessing avian diversity,significant challenges remain,particularly in sampling strategies,DNA extraction methodology,primer selection,and ascertain abundance.Additionally,we discussed the factors influencing the production,transportation,and degradation of avian e DNA in the environment.Finally,we suggested future research directions,including optimizing sampling strategies,developing avian-specific universal primers,expanding avian DNA barcode databases,enhancing e DNA detectability,and integrating environmental RNA(e RNA)and e DNA approaches.展开更多
Implosive collapsing for spherical metal shells is a kind of dynamic compressing method, in which high pressure and high compression degree of materials can be attained. In present work, the dynamic process of implosi...Implosive collapsing for spherical metal shells is a kind of dynamic compressing method, in which high pressure and high compression degree of materials can be attained. In present work, the dynamic process of implosive collapsing for spherical metal shells was regard as spherical symmetry ideally, so one-dimensional spherical symmetric fluid dynamics conservation equations were established, and the finite difference schemes for solving these equations were given. An aluminum spherical shell was assumed, whose inner radius is 4cm and thickness is 2 cm. In numerical simulation, initial centripetal velocities (800, 1000 and 1200 m/s) were used to make aluminum spherical shell collapse. The simulation results show that during the process of implosive collapsing, the material exhibits a compression-expansion-compression pulsation process, and the internal pressure changes and distribution are consistent with the theoretical expectations. The simulation results can be used as a reference for relevant analysis.展开更多
基金Supported by the Tianjin Key R&D Program(No.21YFSNSN00220)。
文摘The flux of dissolved inorganic nitrogen(DIN),predominantly nitrate(NO_(3)^(-))and ammonium(NH_(4)^(+)),from land to coastal waters via rivers is commonly estimated simply by multiplying water flux with nitrogen concentration.Understanding DIN fluxes in gated estuaries is critical as these systems often serve as hotspots for nutrient transformations,influencing coastal water quality and ecosystem health.However,the subsequent interactions involving NO_(3)^(-)and NH_(4)^(+)adsorption or desorption on suspended sediments are often overlooked.To better understand the impact of these interactions on the overall NO_(3)^(-)and NH_(4)^(+)sorption or desorption and subsequently,the mobility and transport to the coastal zone,we conducted a series of NO_(3)^(-)and NH_(4)^(+)adsorption and desorption experiments.These experiments involved varying suspended sediment concentrations,particle sizes,salinities,and sea-salt ions to assess their potential effects.Results indicate that desorption of NO_(3)^(-)and NH_(4)^(+)from suspended sediments is more prominent than adsorption,with NH_(4)^(+)desorption being particularly significant.Notably,at low suspended particle concentrations and high salinity,NH_(4)^(+)desorption from sediments increased markedly,which further amplified in polyhaline conditions.This effect could result from ion pairing between NH_(4)^(+)and seawater anions,along with competition from seawater cations for sediment cation exchange sites,enhancing NH_(4)^(+)diffusion from estuarine sediments,and the elevated NH_(4)^(+)release could promote DIN transport to nearshore waters,especially in gated estuaries where sediment resuspension occurs.Given the critical role of NH_(4)^(+)in estuarine nitrogen cycling,ignoring these dynamics could lead to underestimations of DIN transport in river-estuary systems.Therefore,incorporating sediment dynamics into DIN flux estimations is crucial for accurately assessing nitrogen transport in gated estuaries.
基金supported by the Key Research and Development Project of Tianjin,China(23YFZCSN00040)。
文摘In recent years,environmental DNA(e DNA)has garnered significant attention as a novel tool in biodiversity monitoring,recognized for its efficiency,convenience,and non-invasiveness.Despite its extensive application in various ecological studies,such as conservation,invasion biology,biomonitoring and biodiversity survey assessment,its use in avian monitoring remains in its infancy.This review critically examines the potential and limitations of e DNA technology for avian monitoring,focusing on current advancements and ongoing challenges in this emerging field.Water and air are the primary environmental media for collecting avian e DNA,although other sources like spider webs and plant flowers have been explored as well.Notably,airborne e DNA has been reported to capture the highest diversity of avian species.While avian e DNA technology has shown promise for monitoring rare and endangered species and assessing avian diversity,significant challenges remain,particularly in sampling strategies,DNA extraction methodology,primer selection,and ascertain abundance.Additionally,we discussed the factors influencing the production,transportation,and degradation of avian e DNA in the environment.Finally,we suggested future research directions,including optimizing sampling strategies,developing avian-specific universal primers,expanding avian DNA barcode databases,enhancing e DNA detectability,and integrating environmental RNA(e RNA)and e DNA approaches.
文摘Implosive collapsing for spherical metal shells is a kind of dynamic compressing method, in which high pressure and high compression degree of materials can be attained. In present work, the dynamic process of implosive collapsing for spherical metal shells was regard as spherical symmetry ideally, so one-dimensional spherical symmetric fluid dynamics conservation equations were established, and the finite difference schemes for solving these equations were given. An aluminum spherical shell was assumed, whose inner radius is 4cm and thickness is 2 cm. In numerical simulation, initial centripetal velocities (800, 1000 and 1200 m/s) were used to make aluminum spherical shell collapse. The simulation results show that during the process of implosive collapsing, the material exhibits a compression-expansion-compression pulsation process, and the internal pressure changes and distribution are consistent with the theoretical expectations. The simulation results can be used as a reference for relevant analysis.
